Add support for creating reader conditionals

CHANGELOG.md

@@ -5,6 +5,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Added
+ * Added support for constructing a data representation of reader conditionals (#1125)
+
 ### Fixed
  * Fix a bug where `basilisp test` command fails due to an invalid `argparse` configuration (#1119)
  * Fix a bug where `basilisp.walk/walk` (and any functions that depend on it) did not preserve collection metadata (#1123)

docs/reader.rst

@@ -537,7 +537,7 @@ In nearly all cases, this will be the return value from a macro function, which
 
    :ref:`macros`
 
-.. _reader_conditions:
+.. _reader_conditionals:
 
 Reader Conditionals
 -------------------
@@ -572,6 +572,10 @@ Splicing reader conditionals may only appear within other collection literal for
     basilisp.user=> #?@(:lpy [1 2 3])
     basilisp.lang.reader.SyntaxError: Unexpected reader conditional
 
+.. seealso::
+
+   :lpy:fn:`reader-conditional`, :lpy:fn:`reader-conditional?`
+
 .. _python_version_reader_features:
 
 Python Version Reader Features

src/basilisp/core.lpy

@@ -547,14 +547,25 @@
     v
     (.-name v)))
 
+(defn ^:inline reader-conditional
+  "Construct a data representation of a :ref:`reader conditional <reader_conditionals>`.
+
+  The form must contain balanced key-value pairs."
+  [form is-splicing?]
+  (basilisp.lang.reader/ReaderConditional form is-splicing?))
+
+(defn ^:inline reader-conditional?
+  "Return true if the value is the data representation of a :ref:`reader conditional <reader_conditionals>`."
+  [o]
+  (instance? basilisp.lang.reader/ReaderConditional o))
+
 (defn ^:inline tagged-literal
-  "Construct a data representation of a tagged literal from a
-  tag symbol and a form."
+  "Construct a data representation of a tagged literal from a tag symbol and a form."
   [tag form]
   (basilisp.lang.tagged/tagged-literal tag form))
 
 (defn ^:inline tagged-literal?
-  "Return true if the value is the data representation of a tagged literal"
+  "Return true if the value is the data representation of a tagged literal."
   [o]
   (instance? basilisp.lang.tagged/TaggedLiteral o))
 

src/basilisp/lang/reader.py

@@ -72,7 +72,8 @@
 fn_macro_args = re.compile("(%)(&|[0-9])?")
 unicode_char = re.compile(r"u(\w+)")
 
-DataReaders = Optional[lmap.PersistentMap]
+DataReaderFn = Callable[[Any], Any]
+DataReaders = lmap.PersistentMap[sym.Symbol, DataReaderFn]
 GenSymEnvironment = MutableMapping[str, sym.Symbol]
 Resolver = Callable[[sym.Symbol], sym.Symbol]
 LispReaderFn = Callable[["ReaderContext"], LispForm]
@@ -348,7 +349,7 @@ def _raise_unknown_tag(s: sym.Symbol, v: LispReaderForm) -> NoReturn:
 
 
 class ReaderContext:
-    _DATA_READERS = lmap.map(
+    _DATA_READERS: DataReaders = lmap.map(
         {
             sym.symbol("inst"): _inst_from_str,
             sym.symbol("py"): _py_from_lisp,
@@ -394,7 +395,7 @@ def __init__(  # pylint: disable=too-many-arguments
         self._eof = eof
 
     @property
-    def data_readers(self) -> lmap.PersistentMap:
+    def data_readers(self) -> DataReaders:
         return self._data_readers
 
     @property
@@ -487,6 +488,13 @@ def __init__(
         self._feature_vec = self._compile_feature_vec(form)
         self._is_splicing = is_splicing
 
+    def __eq__(self, other):
+        if self is other:
+            return True
+        if not isinstance(other, ReaderConditional):
+            return NotImplemented
+        return self._form == other._form and self._is_splicing == other._is_splicing
+
     @staticmethod
     def _compile_feature_vec(form: IPersistentList[tuple[kw.Keyword, ReaderForm]]):
         found_features: set[kw.Keyword] = set()

src/basilisp/lang/runtime.py

@@ -2434,7 +2434,7 @@ def in_ns(s: sym.Symbol):
             {
                 _DOC_META_KEY: (
                     "The set of all currently supported "
-                    ":ref:`reader features <reader_conditions>`."
+                    ":ref:`reader features <reader_conditionals>`."
                 )
             }
         ),

src/basilisp/lang/tagged.py

@@ -15,10 +15,7 @@
 _FORM_KW = keyword("form")
 
 
-class TaggedLiteral(
-    ILispObject,
-    ILookup[K, T],
-):
+class TaggedLiteral(ILispObject, ILookup[K, T]):
     """Basilisp TaggedLiteral. https://clojure.org/reference/reader#tagged_literals"""
 
     __slots__ = ("_tag", "_form", "_hash")

tests/basilisp/test_core_fns.lpy

@@ -461,8 +461,6 @@
   (is (= 1 (rand-nth [1])))
   (is (#{1 2} (rand-nth [1 2]))))
 
-
-
 (deftest subvec-test
   (is (= [] (subvec [] 0)))
   (is (thrown? python/IndexError (subvec [] 3)))

tests/basilisp/test_core_reader_utility_fns.lpy

@@ -0,0 +1,68 @@
+(ns tests.basilisp.test-core-reader-utility-fns
+  (:require
+   [basilisp.test :refer [deftest is testing]]))
+
+(deftest reader-conditional-test
+  (let [form         '()
+        is-splicing? true
+        reader-cond  (reader-conditional form is-splicing?)]
+    (testing "equality"
+      (is (= reader-cond reader-cond))
+      (is (= reader-cond (reader-conditional form is-splicing?)))
+      (is (not= reader-cond (reader-conditional '(:clj [] :lpy [true]) is-splicing?)))
+      (is (not= reader-cond (reader-conditional form false))))
+
+    (testing "accessors"
+      (is (= form (:form reader-cond)))
+      (is (= is-splicing? (:splicing? reader-cond)))
+      (is (nil? (:key reader-cond)))
+      (is (= ::default (:key reader-cond ::default))))
+
+    (testing "predicate"
+      (is (true? (reader-conditional? reader-cond)))
+      (is (false? (reader-conditional? nil)))
+      (is (false? (reader-conditional? 0)))
+      (is (false? (reader-conditional? ::foo))))
+
+    (testing "printing"
+      (is (= "#?@()" (pr-str reader-cond)))
+      (is (= "#?()" (pr-str (reader-conditional '() false))))
+      (is (= "#?@(:clj [] :lpy [true])" (pr-str (reader-conditional '(:clj [] :lpy [true]) true)))))
+
+    (testing "validation"
+      (is (thrown? basilisp.lang.reader/SyntaxError
+                   (reader-conditional '(:clj) true)))
+      (is (thrown? basilisp.lang.reader/SyntaxError
+                   (reader-conditional '(:clj [] :lpy) true)))
+      (is (thrown? basilisp.lang.reader/SyntaxError
+                   (reader-conditional '('lpy [] :clj [true]) true))))))
+
+(deftest tagged-literal-test
+  (let [tag 'tag
+        form 1
+        tagged (tagged-literal tag form)]
+    (testing "equality"
+      (is (= tagged tagged))
+      (is (= tagged (tagged-literal tag form)))
+      (is (not= tagged (tagged-literal 'foo form)))
+      (is (not= tagged (tagged-literal tag 2))))
+
+    (testing "accessors"
+      (is (= tag (:tag tagged)))
+      (is (= form (:form tagged)))
+      (is (nil? (:key tagged)))
+      (is (= ::default (:key tagged ::default))))
+
+    (testing "predicate"
+      (is (true? (tagged-literal? tagged)))
+      (is (false? (tagged-literal? nil)))
+      (is (false? (tagged-literal? 0)))
+      (is (false? (tagged-literal? ::foo))))
+
+    (testing "printing"
+      (is (= "#tag 1" (pr-str tagged)))
+      (is (= "#js []" (pr-str (tagged-literal 'js []))))
+      (is (= "#js {}" (pr-str (tagged-literal 'js {})))))
+
+    (testing "validation"
+      (is (thrown? TypeError (tagged-literal 1 1))))))